1. Field of the Invention
The present invention relates to an ink composition for ink jet recording.
2. Background Art
Ink jet recording is a printing method wherein droplets of an ink composition are ejected and deposited onto a recording medium such as paper. This method has a feature that an image having a high resolution and a high quality can be printed at a high speed with a relatively inexpensive apparatus. In general, the ink composition used in the ink jet recording comprises water as a main component and, added thereto, a colorant and a wetting agent, such as glycerin, for prevention of clogging and other purposes.
Dyes and pigments are generally used as the colorant. The dyes are extensively used by virtue of good water solubility. Good water solubility of the dyes, however, results in deteriorated waterproofness of printed images. On the other hand, the pigments are essentially insoluble in water, realizing prints having excellent waterproofness. The pigments, however, should be stably dispersed in an ink composition and, in some cases, offer prints having inferior scratch resistance to the prints formed by using dyes. Further, printing using an ink composition containing a pigment as a colorant often suffers from uneven printing. The uneven printing refers to a variation in color density in the print derived from localization of a colorant on the paper. Although the uneven printing poses no significant problem in printing of letters of regular size, it is a serious problem in applications where figures, graphs and the like are printed.